This application is based on Japanese Patent Application Nos. 10-322878 (1998) filed Oct. 27, 1998, 10-322879 (1998) filed Oct. 27, 1998, 10-322880 (1998) filed Oct. 27, 1998, 10-311050 (1998) filed Oct. 30, 1998, the contents of which are incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to an electro-thermal conversion device board which includes an electro-thermal conversion device layer having a plurality of heat generation parts arranged corresponding to a liquid flow passage for conducting a liquid used for recording, an ink-jet recording head provided with the electro-thermal conversion device board, an ink-jet recording apparatus using the same, and a production method of an ink-jet recording head.
2. Description of the Related Art
In general, an ink-jet recording apparatus is provided with a recording head for ejecting an ink as a liquid used for recording. A bubble-jet type recording head, as shown in, for example, Japanese Patent Application Laid-open Nos. 62-261452 (1987) and 62-261453 (1987), comprises an ink ejection member having an ink ejection port forming surface on which a plurality of ink ejection ports for ejecting ink drops are formed at a predetermined interval, an electro-thermal conversion device board having electro-thermal conversion device layers arranged corresponding to respective ink flow passages communicating with respective ink eject ports, and a printed circuit board for supplying drive control signals to the respective electro-thermal conversion device layers of the electro-thermal conversion device board.
The ink ejection member is provided with a common liquid chamber which stores a predetermined amount of ink supplied from an ink tank. The common liquid chamber is communicated with an end of each ink flow passage formed by a partition wall member disposed in parallel and opposite to each other. Accordingly, this distributes the ink from the common liquid chamber to respective ink flow passages, which is ejected as an ink droplet from the ink ejection port.
In the electro-thermal conversion device board, for a multi-value recording system in which the size of ejected liquid-droplet is changed according to a multi-value recording image data, one is proposed in which a plurality of heat generation parts of a plurality of electro-thermal conversion device layers are respectively driven selectively.
The electro-thermal conversion device board, for example, as shown in FIGS. 17A and 17B, comprises a base table part 6 in which is disposed between an ink flow passage 2ai of the ink ejection member and a printed circuit board (not shown) of the electro-thermal conversion device layer, and a heat generation part 8ai (i=1 to n, n is an integer) and heat generation part 20ai (i=1 to n, n is an integer) of the electro-thermal conversion device layer are disposed on one of the surfaces according to each ink flow passage, a discrete electrode layer 10 with one end thereof electrically connected to the heat generation part 8ai, a discrete electrode layer 18 is flush with the discrete electrode layer 10 and having one end thereof electrically connected to the heat generation part 20ai, a common electrode layer 12 in which one end is electrically connected respectively to the heat generation part 8ai and the heat generation part 20ai and formed on the same plane as of the discrete electrode layers 10 and 18, a protective layer 16 covering all of the adjacent heat generation parts 8ai and 20ai, the discrete electrode layer 10, and the discrete electrode layer 18, and a cavitation resistant layer 14 covering the entire surface of the protective layer 16.
In FIGS. 17A and 17B, parts corresponding to the two ink flow passages 2ai (i=1 to n, n is an integer)of the ink ejection member are shown representatively, and other parts are omitted.
The heat generation part 8ai and the heat generation part 20ai are disposed on a common straight line along the same ink flow passage on the same plane of the base table part 6. The heat generation part 8ai is disposed at a position closer to the ink ejection port of the ink ejection member than the heat generation part 20ai. The capacity (heat generation amount) of the heat generation part 8ai is smaller than the capacity (heat generation amount) of the heat generation part 20ai. 
The other end of the common electrode layer 12 formed on the heat generation part 8ai and the heat generation part 20ai is connected with a reference power supply for supplying a predetermined power.
The cavitation resistant layer 14 formed with a rough surface has shallow grooves correspondingly between respective partition wall members 4ai (i=1 to n, n is an integer) of the ink ejection member and also has elongate grooves 14a correspondingly to respective partition wall members 4ai. 
Adjacent ink flow passages 2ai are formed independently without communication with each other by closely contacting one end of the partition wall member 4ai of the ink ejection member with the cavitation resistant layer 14 at a predetermined pressure.
In this case, the number of ink ejection ports has a tendency to increase recently in compliance to the requirement for high resolution of the resulting recording images, and therefore, in view of obtaining a compact recording head, the distance between adjacent ink flow passages and the distance between adjacent heat generation parts 8ai and heat generation parts 20ai also tend to be decreased.
When, as described above, a plurality of heat generation parts 8ai and heat generation parts 20ai are formed on a same straight line for each ink flow passage, and the discrete electrode layers 10 and 18 and the common electrode layer 12 are formed in parallel on a same plane, wiring between respective electrode layers and the reference power supply becomes complicated and relatively increased.
Further, when the number of ink ejection ports is increased to enhance image density, it is also considered that widths of the respective heaters, the discrete electrode layers 10 and 18, and the common electrode layer 12 are decreased to reduce the width of each ink flow passage. However, by decreasing the width of each heat generation part, there is a danger of deteriorating the heating efficiency and ink ejection performance, and still further, decrease in width of the discrete electrode layers 10 and 18 and the common electrode layer 12 has a certain limitation because of an increase in wiring resistance. Therefore, increased density of heat generation parts of the electro-thermal conversion device board and increased density of ink ejection ports and a compact electro-thermal conversion device board are not easy to realize.
In view of the above problems, a first object of the present invention is to provide an electro-thermal conversion device board having a plurality of heat generation parts arranged corresponding to liquid flow passages for conducting a liquid used for recording, an ink-jet recording head provided with an electro-thermal conversion device board, an ink-jet recording apparatus using the recording head, and a production method of the ink-jet recording head which is capable of providing high-density heaters of the electro-thermal conversion device board and ink ejection ports and a compact electro-thermal conversion device board, an ink-jet recording head provided with the electro-thermal conversion device board without deteriorating ink ejection performance.
Further, when making multi-value recording as described above, the bubble generation power is controlled by selectively changing the area of the driven electro-thermal conversion device. Therefore, the bubble generation power when forming a small liquid droplet is substantially small compared to a bubble generation power when only a single electro-thermal conversion device is disposed in one flow passage. In such a state, if there is a gap such that generates a crosstalk between flow passages, since a bubble generation power sufficient for ejection is difficult to be obtained because of an energy loss due to the crosstalk, there may be a case in which a desired liquid ejection cannot be made in a small liquid droplet ejection mode.
Here, it is also considered to increase the area of the electro-thermal conversion device used for ejecting small liquid droplets in order to reduce the effect of crosstalk, however, in this case, difference in ejection amount caused by respective combinations of a plurality of electro-thermal conversion devices in multi-value recording is decreased, which is not preferable.
Therefore, an ink-jet recording head in which a plurality of electro-thermal conversion devices are disposed in the flow passage for making multi-value recording is preferably provided on the board with a recess part engaging with a flow passage wall as described in Japanese Patent Application Laid-open No.7-89073 (1995) for the purpose of preventing crosstalk.
However, when flow passages are arranged in a high density in a construction in which a plurality of electro-thermal conversion devices are disposed in a single flow passage, it is difficult to form a sufficient depth of the recess part as has been performed in the past. That is, when the height of a discrete heat accumulation layer is increased to increase the depth of the recess part, wiring provided on top thereof (film formation of a wiring material in a stepped part) becomes difficult, resulting in deterioration of reliability. Further, it is also considered that the electro-thermal conversion device is disposed out of the recess part, however, decrease in width of wiring electrode has a certain limit since it results in an increase in wiring resistance and, since a plurality of electro-thermal conversion devices are provided in the flow passage which results in a increased number of wiring electrodes which is difficult to be achieved in a layout on a flat (two-dimensional) surface.
In consideration of the above problems, a second object of the present invention is to provide an electro-thermal conversion device board, an ink-jet recording head provided with the electro-thermal conversion device board, an ink-jet recording apparatus using the same and a production method of the ink-jet recording head which can provide a sufficient depth of a recess part for engaging with a flow passage wall and is superior in reliability of wiring electrodes.
In accordance with the present invention which attains the above objects, there is provided an electro-thermal conversion device board comprising electro-thermal conversion device layers having a plurality of heat generation parts arranged on a straight line corresponding to a plurality of liquid flow passages formed at one end side with liquid discharge ports for discharging a liquid used for recording, discrete electrode layers electrically connected respectively to the plurality of heat generation parts of the electro-thermal conversion device layer, common electrode layers formed stackedly through an insulation layer beneath the electro-thermal conversion device layers and the discrete electrode layers and electrically connected to the plurality of heat generation parts of the electro-thermal conversion devices, and a substrate part provided thereon with the electro-thermal conversion device layers, the discrete electrode layers and the common electrode layers.
The ink-jet recording head according to the present invention comprises a liquid discharge member having a plurality of liquid flow passages respectively formed at one end side with liquid discharge ports for discharging a liquid used for recording, electro-thermal conversion device layers having at one end side thereof a plurality of heat generation parts arranged on a straight line respectively corresponding to liquid flow passages provided with liquid discharge ports formed at one end side thereof for discharging a liquid used for recording, discrete electrode layers electrically connected respectively to the plurality of heat generation parts of the electro-thermal conversion device layers, common electrode layers formed in a stack through an insulation layer beneath the electro-thermal conversion device layers and the discrete electrode layers electrically connected respectively to the plurality of heat generation parts of the electro-thermal conversion devices, an electro-thermal conversion device board provided thereon with the electro-thermal conversion device layers, the discrete electrode layers and the common electrode layers, and a printed circuit board electrically connected to the electro-thermal conversion device board for supplying power respectively to the common electrode layers of the electro-thermal conversion device board.
The ink-jet recording apparatus according to the present invention comprises the above ink-jet recording head for performing recording operation to a recording surface of a recording medium, recording head moving means for moving the ink-jet recording head relative to the recording surface of the recording medium, and a control part for causing the recording head moving means to perform operation of relative movement of the ink-jet recording head and the ink-jet recording head to perform recording operation.
According to the present invention, since the common electrode layers are formed stackedly through an insulation layer beneath the electro-thermal conversion device layers having a plurality of heat generation parts arranged on a straight line corresponding to a plurality of liquid flow passages and discrete electrode layers and electrically connected respectively to the heat generation parts of the electro-thermal conversion device layers, high-density construction of heaters of the electro-thermal conversion device board and ink ejection ports and compact construction of the electro-thermal conversion device board can be achieved.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.